Houdini 3 contains many evaluation and search improvements in all phases of the game and is about 50 Elo stronger than its predecessor Houdini 2 (which at the time of writing was still unmatched by any other engine). The opening improvements relate mostly to piece mobility and space management and are most convincingly demonstrated by the progress in Fischer Random Chess for which Houdini 3 has become about 75 Elo stronger. In the middle game Houdini 3 has significant enhancements for recognizing pieces with limited mobility and in king-side safety. Houdini 3 will seek deeper in end games and solve more positions than before.

In the new Tactical Mode Houdini 3 will prefer tactical instead of positional solutions. In tactical test suites the Tactical Mode will find more solutions and provide significantly faster solution times, often by a factor of 3 to 10.

The Accelerated Principal Variation Search or “Smart Fail-High” is especially useful in very deep analysis when a different move becomes best at very high search depth. Houdini 3 will apply an automatic depth reduction that often speeds up finding the Principal Variation by a factor of 5 to 10.

Besides Nalimov and Gaviota End Game Table Bases, Houdini 3 now also supports Scorpio bitbases. These bitbases are loaded in memory when the program starts (requiring about 300 MB of memory) and are then readily available to the engine.

Hash usage has been optimized, improving back-tracking analysis. Houdini 3 Pro will now support hash tables up to 256 GB.

The engine evaluations have been carefully recalibrated so that +1.00 pawn advantage gives a 80% chance of winning the game against an equal opponent at blitz time control. At +2.00 the engine will win 95% of the time, and at +3.00 about 99% of the time. If the advantage is +0.50, expect to win nearly 50% of the time.

Fun fact: Over 10 million chess games were played for the development and tuning of Houdini 3!